Blade Servers, Virtualization Can Tax Data Center Facility Capacity

Continued innovation in computer technology is pushing the facility management and information technology (IT) departments closer together. As servers become more compact, they take up less space, but at the same time they require many more kilowatts of energy to power them.

The appetite for energy creates the need for more space in the data center to house the facility infrastructure that keeps the computers from going down. In a data center, "white space" refers to the usable space, measured in square feet, where computer cabinets are housed. The amount of space needed by computers is getting smaller in part because servers are much thinner, allowing more to fit in less space.

"Companies can now incorporate blade servers, which can hold up to 42 servers per rack," says Paul E. Schlattman, vice president, mission critical facilities group, Environmental Systems Design. The new servers may now need only two racks where old servers would have needed 10.

Servers may also need less physical space because of virtualization, says Schlattman. Virtualization allows a server to run multiple platforms. In the past each server would use only 8 to 10 percent of its capacity, because it would run only a specific type of software. With virtualization, on the other hand, servers can run multiple platforms, "so now my server is running at 80 percent of its capacity," says Schlattman. "This also increases the need for power, because the (server) is running hotter." Although the blade rack requires more power than a normal rack, overall the data center will save both space and energy by using the blade rack.

Those IT-side developments have huge implications for the data center facility infrastructure. As density increases, so does the need for support infrastructure: power transformers, uninterruptible power supply (UPS) systems, computer room air conditioners (CRACs) and chillers, and air distribution systems. In the highest tier data centers, support infrastructure may occupy four to six times the amount of space needed to house the computers. The higher the kilowatt load the computers are supporting, the more the infrastructure will be needed.

The increases in density have been significant, says R. Stephen Spinazzola, vice president, RTKL Associates. "Ten years ago, 500 kilowatts [of power] was considered to be robust; today 1,000 to 5,000 kilowatts of power is robust," he says. Clearly, the amount of square footage needed, in terms of infrastructure, to support 5,000 kilowatts of power will be much greater than the space needed to support computers running on less power.

A single computer cabinet may have been powered by one kilowatt 10 years ago, but it now uses 50 kilowatts. "It is hard to distribute that much power and cooling in a small space," Spinazzola says. The most common mistake in legacy data centers is to keep "migrating technology," or increasing computing power in the same amount of space, without thinking about how the facility can supply all that power and cooling to support the increased IT load, Spinazzola says.